U.S. Pat. No. 6,200,644 (Ulfstedt et al.) purports to disclose methods for manufacturing liquid-tight and gas-tight packaging board, and a package and products provided according to the said methods. According to the invention, a polymerizing reaction mixture is spread on paper or a board base of paperboard or cardboard, the mixture containing at least one silicon compound forming an inorganic, chain or cross-linked polymeric backbone containing alternating silicon and oxygen atoms, and at least one reactive, organic compound forming organic side chains and/or crosslinks in the polymeric backbone. The reaction mixture may form a colloidal solution in which, along with the polymerization, gelling takes place, whereupon the thus created gel is dried, densified and cured to form a liquid-tight and gas-tight layer of coating. In addition to oxygen and silicon, the said chain-like or cross-linked polymeric backbone can contain metal atoms which replace the silicon, and the organic compound can contain, as a reactive group, an epoxy, an amino, a carboxyl, a carbonyl, a vinyl or a methacrylate group. Furthermore, a joint-forming polymeric coating can be spread on the previously obtained, tight glassy layer of coating to close the manufactured package. Products, to which the paper or the board coated according to the invention can be applied, include milk and juice containers or similar packages of liquid foodstuffs, bag-type foodstuff packages, heat-sealed, peelable covers of containers and boxes, and microwave and conventional oven trays.